Motoichi Ohtsu's research while affiliated with Tokyo Institute of Technology and other places
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Publications (9)
Let us investigate an example of a practical nanometer-resolution scanning nearfield optical microscope (NOM). An NOM setup is shown in Fig. 2.1, and a recipe for preparing and operating the system is listed below. Several examples of such a system are given in Chapter 3, optical probes are described in Chapter 4, and experimental results showing e...
Figure 3.1 explains the basic concept of a near-field optical microscope (NOM). Figure 3.1a shows how an evanescent field is generated on the surface of a subwavelength-size sample sphere. The volume of the evanescent field depends on the size of the sample, as described in Section 2.4.3 (see Fig. 2.6). Since an evanescent field is nonradiative, it...
In this chapter, we study the theoretical background of optical near-field problems involving near-field optical microscopy (NOM). As discussed in previous chapters, NOM involves complicated optical processes consisting of subsystems of different characteristic scales of the electromagnetic interaction. In other words, in NOM both microscopic and m...
Conventional photonic devices are too large for use in the NOM because they are larger than the optical wavelength, although the NOM is useful for their study. In contrast, the NOM is indispensable for the study of semiconductor quantum structures. Take, for example, the case of a quantum dot. Using conventional optical techniques it is impossible...
In this chapter, we study the basic electromagnetic processes involved in near-field optical microscopes (NOM) from the theoretical viewpoint of the multiple scattering of a vector field. The purpose is to examine the localization of the near-field interaction between small dielectric objects. Such a process is relevant to the near-field detection...
Nonlinear optical phenomena can be induced by utilizing the high optical energy density of the evanescent field, which can lead to the processing of nanometric areas of material surfaces, the fabrication of nanometric optical functional devices, and nanometric photolithography. As an example of realizing photonic devices with nanometric dimensions,...
As described in Section 3.1, the probe is the most essential component governing the performance of the NOM. Since the size of the probe tip is of the order of nanometers, special advanced fabrication processes have had to be developed. Fabrication methods such as pulling heated glass capillaries [1] and sharpening quartz rods or optical fibers by...
With regard to superresolution of the NOM beyond the diffraction limit, it has been pointed out in Section 2.4.3 that the confinement of a three-dimensional evanescent field on a sub wavelength object strongly depends on its size and topography. The approach of a sharpened probe tip to a single object with precise positioning enables one to obtain...
Citations
... To overcome these restrictions, fluorescent semiconductor nanocrystals (also known as quantum dots) have been tested in most biotechnological applications, including DNA array technology (Dubertret 2005) and immunofluorescence assays for cellular or animal tissues analysis (Dubertret et al. 2002, Medintz et al. 2005. In 2003, the scanning near-field optical microscope (SNOM) was developed and utilized to study the membrane activity in a live cell sample (Sasaki 2003). Near-field optical microscope can detect tiny vertical movements on the cell membrane in the range of one nm or less, a resolution about three orders of magnitude superior than conventional optical microscopes. ...
Reference: Nano-biosensors: A Custom-built Diagnosis
... 19,20 Some cells may have attached, but at a level below the refractive index limit of detection of the LPG sensor (estimated to be 0.001 refractive index units). [54][55][56] The detection of bacteria by the sensor was limited to the region of the evanescent field, [39][40][41][42] which, for the sensors used in this study, was greater than 0.5 µm from the cladding surface (see ESI, † 'LPG optical fibre sensor considerations'). However, the ability of the sensor to detect biofilm formation beyond the evanescent field (which encompasses most of the biomass detected) could be due to larger colonies introducing a third waveguide (other than the core and cladding), which created another coupling condition. ...
